Gas-Phase Ion Chemistry of Oxalyl Chloride: An Electron Bombardment Matrix Isolation FTIR Spectroscopic Study

The gas-phase ion chemistry of oxalyl chloride has been studied by bombardment of dilute mixtures of oxalyl chloride in rare gases with fast electrons followed by isolation of the decomposition products in the diluent rare gases at 12 K. The major products observed in the matrix by FTIR absorption spectroscopy are phosgene, carbonyl chloride radical, and carbon monoxide. Some CCl was observed when the diluent gas was argon. No ions were identified in the matrix, and it is proposed that the initially isolated ions are neutralized by secondary electrons impinging on the positively biased matrix. A change in the relative intensities of products was observed when the diluent rare gas was changed from argon to krypton and when the mixture was doped with varying concentrations of CO or N2. These doping experiments give direct evidence for at least two mechanisms for formation of the carbonyl chloride cation, one of which involves secondary decomposition of phosgene radical cation. The products obtained here are compared with those obtained by EI mass spectrometry. It is suggested that the different product intensities observed in EI and CE mass spectra are due to the fact that product decomposition is efficiently quenched in the source following CE ionization.